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Unprotect-CmsMessage

  • Reference
Module:
Microsoft.PowerShell.Security

Decrypts content that has been encrypted by using the Cryptographic Message Syntax format.

Syntax

Unprotect-CmsMessage
         [-EventLogRecord] <EventLogRecord>
         [[-To] <CmsMessageRecipient[]>]
         [-IncludeContext]
         [<CommonParameters>]
Unprotect-CmsMessage
         [-Content] <string>
         [[-To] <CmsMessageRecipient[]>]
         [-IncludeContext]
         [<CommonParameters>]
Unprotect-CmsMessage
         [-Path] <string>
         [[-To] <CmsMessageRecipient[]>]
         [-IncludeContext]
         [<CommonParameters>]
Unprotect-CmsMessage
         [-LiteralPath] <string>
         [[-To] <CmsMessageRecipient[]>]
         [-IncludeContext]
         [<CommonParameters>]

Description

The Unprotect-CmsMessage cmdlet decrypts content that has been encrypted using the Cryptographic Message Syntax (CMS) format.

The CMS cmdlets support encryption and decryption of content using the IETF standard format for cryptographically protecting messages, as documented by RFC5652.

The CMS encryption standard uses public key cryptography, where the keys used to encrypt content (the public key) and the keys used to decrypt content (the private key) are separate. Your public key can be shared widely, and isn't sensitive data. If any content is encrypted with this public key, only your private key can decrypt it. For more information, see Public-key cryptography.

Unprotect-CmsMessage decrypts content that has been encrypted in CMS format. You can run this cmdlet to decrypt content that you have encrypted by running the Protect-CmsMessage cmdlet. You can specify content that you want to decrypt as a string, by the encryption event log record ID number, or by path to the encrypted content. The Unprotect-CmsMessage cmdlet returns the decrypted content.

Support for Linux and macOS was added in PowerShell 7.1.

Examples

Example 1: Decrypt a message

In the following example, you decrypt content that's located at the literal path C:\Users\Test\Documents\PowerShell. For the value of the required To parameter, this example uses the thumbprint of the certificate that was used to perform the encryption. The decrypted message, "Try the new Break All command," is the result.

$parameters = @{
  LiteralPath = "C:\Users\Test\Documents\PowerShell\Future_Plans.txt"
  To = '0f 8j b1 ab e0 ce 35 1d 67 d2 f2 6f a2 d2 00 cl 22 z9 m9 85'
}
Unprotect-CmsMessage -LiteralPath @parameters

Try the new Break All command

Example 2: Decrypt an encrypted event log message

The following example gets an encrypted event from the PowerShell event log and decrypts it using Unprotect-CmsMessage.

$event = Get-WinEvent Microsoft-Windows-PowerShell/Operational -MaxEvents 1 |
    Where-Object Id -eq 4104
Unprotect-CmsMessage -EventLogRecord $event

Example 3: Decrypt encrypted event log messages using the pipeline

The following example gets all encrypted events from the PowerShell event log and decrypts them using Unprotect-CmsMessage.

Get-WinEvent Microsoft-Windows-PowerShell/Operational |
    Where-Object Id -eq 4104 |
    Unprotect-CmsMessage

Parameters

-Content

Specifies an encrypted string, or a variable containing an encrypted string.

Type:String
Position:0
Default value:None
Required:True
Accept pipeline input:True
Accept wildcard characters:False

-EventLogRecord

Specifies an event log record that contains a CMS encrypted message.

Type:PSObject
Position:0
Default value:None
Required:True
Accept pipeline input:True
Accept wildcard characters:False

-IncludeContext

Type:SwitchParameter
Position:Named
Default value:None
Required:False
Accept pipeline input:False
Accept wildcard characters:False

-LiteralPath

Specifies the path to encrypted content that you want to decrypt. Unlike Path, the value of LiteralPath is used exactly as it's typed. No characters are interpreted as wildcard characters. If the path includes escape characters, enclose it in single quotation marks. Single quotation marks tell PowerShell not to interpret any characters as escape sequences.

Type:String
Position:0
Default value:None
Required:True
Accept pipeline input:False
Accept wildcard characters:False

-Path

Specifies the path to encrypted content that you want to decrypt.

Type:String
Position:0
Default value:None
Required:True
Accept pipeline input:False
Accept wildcard characters:False

-To

Specifies one or more CMS message recipients, identified in any of the following formats:

  • An actual certificate (as retrieved from the certificate provider).
  • Path to the a file containing the certificate.
  • Path to a directory containing the certificate.
  • Thumbprint of the certificate (used to look in the certificate store).
  • Subject name of the certificate (used to look in the certificate store).
Type:CmsMessageRecipient[]
Position:1
Default value:None
Required:False
Accept pipeline input:False
Accept wildcard characters:False

Inputs

EventLogRecord

String

You can pipe an object containing encrypted content to this cmdlet.

Outputs

String

This cmdlet returns the unencrypted message.